Thermal snap-action switch



.1962 F. N. ANDERSON 3,019,319

THERMAL SNAP-ACTION SWITCH Filed Aug. 5, 1959 INVENTOR. 1,250 A! Jwmsm/ United States Patent 3,019,319 THERMAL SNAP-ACTION SWITCH Fred N. Anderson, Highland Park, Ill., assignor to Cherry Electrical Products Corp., Highland Park, 11]., a corporation of Illinois Filed Aug. 3, 1959, Ser. No. 831,143 1 Claim. (Cl. 200-422) This invention relates to a new and useful improvement in a thermal snap-action switch and more particularly to a heat responsive switch wherein the contact carrying member is moved with a snap-action.

Another object of my invention is the provision in a switch of this character in which the switch contact actuating member is a bi-metal contact arm and is moved in a snap-action in response to a heat expelling member.

A further objectof this invention is in the provision in a switch of this character, of a thermistor for actuating a bi-metal contact arm.

Another object of this invention is in the provision in a switch of this character of an arrangement of parts which is simple and economical in manufacture.

Other objects will appear hereinafter.

The invention consists in the novel combination and arrangement of parts to be hereinafter described and claimed.

The invention will be best understood by reference to the accompanying drawings showing the preferred form of construction, and in which:

FIG. 1 is a side elevational sectional view of my improved thermal snap-action switch;

FIG. 2 is a front elevational sectional view of my improved thermal snap-action switch; and

FIG. 3 is a side elevational sectional view of a modified form of my improved thermal snap-action switch.

My improved thermal snap-action switch comprises a substantially fiat rectangular shaped base 10. The top surface of the base is provided with a recess 11. The side walls of the recess 11 are formed to provide a shoulder 12 as seen in FIGS. 1 and 2. A thermistor 13 is adapted to be placed in the recess 11 so that the marginal edges thereof sit upon the shoulder 12.

The base 10 is provided with a plurality of slots 14 and 15. In the slot 14 is frictionally seated a contact bracket 16. This bracket 16 provides a medial portion 17 and a raised contact bearing end 18. The contact bracket 16 is connected to the base 10 by a circular band clasp 19, as shown, or by riveting directly to the base 10. Disposed between the top face of the base r 10 and the medial portion 17 of the contact bracket 16 is an insulation plate 20. This insulation plate 20 provides a' portion thereof that extends into the opening of the recess 11 and which is in facial abutment with one edge portion of the thermistor 13 as seen in FIG. 1.

In the slot a terminal arm 21 is adapted to be firmly positioned. This terminal arm 21 provides a hook portion 22 which is bent so as to engage an opposite edge portion of the thermistor 13 with respect to the insulation plate as seen in FIG. 1. By this arrangement it is clearly shown that I have provided a simplified retaining connection for the thermistor 13 with respect to the base 10.

The recess 11 is provided with a slot 23 formed in the bottom wall thereof. In this slot 23 is positioned a spring loaded contact arm 24. This contact arm 24 has a bearing connection with the bottom surface of the thermistor 13 when it is seated upon the shoulder 12.

Extending parallel to the other opposite longitudinal edges of the base 10 are slots 25 and 26. Positioned within the slots 25 and 26 are pivot brackets 27 and 28 respectively.

Each of the pivot brackets 27 and 28 adjacent the top 3,019,319 Patented Jan. 30, 1962 edge thereof and on their inner walls are provided with V-grooves 29 and 30 respectively. Positioned in the V- grooves 29 and 30 are the end portions of a bi-metal contact arm 31. This bi-me'tal contact arm 31 is held in spaced relation with respect to the top edge of the thermistor 13 as viewed in FIGS. 1 and 2. The bimetal contact arm 31 carries a contact member 32 which is adapted to be moved in a manner hereinafter described into an engagement with a contact 33 carried by the free end 18 of the contact bracket 16.

As current is applied to the thermistor 13 such element will give off heat which will be picked-up by the restrained bi-metal contact arm 31 causing the bi-metal contact arm 31 to bend in the direction which it would normally were it not restrained. Since normal bending of the bi-metal contact arm 31 cannot occur by reason of the pivotal brackets 27 and 28, it will deflect such pivotal brackets 27 and 28 in their respective slots 25 and26 in a direction away from each other as the bimetal contact arm 31 assumes its full longitudinal length in a horizontal plane. As the thermal activity continues, the bi-metal contact arm 31 will move away from the thermistor 13 beyond a horizontal plane and be snapped over so that the contact 32 thereof will engage the contact 33. This snap-action of the bi-metal contact arm 31 is accomplished by the buckling forces imposed upon it by the returning of the deflected pivotal brackets 27 and 28 to their normal position as seen in FIG. 2. Since the contact bracket 16 also acts as a stop for the bi-metal contact arm 31, it will allow contact pressure between contacts 32 and 33 to reach a maximum. When current is withdrawn from the thermistor 13 the reverse of the above procedure will occur thereby breaking the contact with the same positive snap-action.

In FIG. 3 I show a modified form of my thermal snapaction switch. In such modified form I provide a housing 34. The base of the housing 34 provides a raised seat 35 for a thermistor 36. One end of the thermistor is held in place by a contact bracket 37 which provides a lateral finger 38 in facial abutment with the top surface of the thermistor 36. Adjacent the opposite end of the thermistor 36 is a contact bracket 39 which has a spring loaded arm 4%] also engaging the upper surface of the thermistor 36 to hold it on the seat 15. Within the housing 34 are two spaced apart upstandting members 41 and 42. A U-shaped pivot bracket 43 is disposed between the upstanding members 41 and 42. One free end of the U-shaped bracket 43 is V-notched as at 44 and receives therein one end 45 of a movable bimetal contact member 46. The opposite end 47 of such member 46 is connected to a portion 48 of the contact arm 37. A terminal 49 is disposed in a slot 50 formed in the housing 34 and provides a longitudinally extending arm 51 extending above and in spaced relation to the thermistor 36. This arm 51 carries a contact 52 which is adapted to be engaged by a contact 53 carried by the bi-metal contact 46. The side walls of the housing 34 provide a rest 54 for the bi-metal contact mem ber 46 when in normal unactuated position as seen in FIG. 3.

The operation of the modified thermal snap-action switch is the same as heretofore described with the exception that it is the free end of the U-shaped bracket 43 which is laterally disposed into the dotted line posi tion as seen in FIG. 3 as the bi-metal contact member 46 is forced to attain its full longitudinal length in a horizontal plane extending between its connection to the bracket 43 and contact bracket 37.

While I have illustrated and described the preferred form of construction for carrying my invention into effect, this is capable of variation and modification without departing from the spirit of the invention. I therefore, do not wish to be limited to the precise details of construction set forth, but desire to avail myself of such variations and modifications as come within the scope of the appended claim.

Having thus described my invention, what I claim as new and desire to protect by Letters Patent is:

, Athermal snap action switch comprising a substantially rectangularly shaped base provided with a plurality ofslots extending transverse of its longitudinal length, with a slot adjacent each edge of said rectangularly shaped base, a heat emitting element carried by said base, a plurality of means carried in certain of the slots formed in said base for connecting said heat emitting element thereto, one of said means carried by certain of said slots providing an electrical conduit to one side of said heat emitting element, while the other of said means provides a fixed switch contact carried above and in spaced relation to said heat emitting element, a thermal responsive switch actuating member carried by said base above and in spaced relation to said heat emitting element, yieldable means carried in certain other of the slots formed in said base for pivotally engaging the opposite ends of said switch actuating member for supporting the same relative to said heat emitting element, with one of said yieldable means providing an electrical conduit for one side of said switch member, said switch actuating member having a longitudinal length greater than the distance between said yieldable means so that said switch actuating member will move with a snaplike action into and out of contact with the fixed contact when said switch actuating member is thermally responsively moved by the heat emitting from said heat emitting element.

References Cited in the file of this patent UNITED STATES PATENTS 267,711 Peck et al Nov. 21, 1882 1,845,998 Gregory Feb. 16, 1932 1,898,174 Dubilier Feb. 21, 1933 2,016,244 Gregory Oct. 1, 1935 2,239,541 Spencer Aug. 22, 1941 2,825,785 Taylor Mar. 4, 1958 FOREIGN PATENTS 318,960 Switzerland Mar. 15, 1957 

